In conventional practice, known examples of ventilators include those that perform mechanical ventilation, having an air discharge fan for forcefully discharging air in an indoor space to an outdoor space, and an air supply fan for forcefully supplying air from the outdoor space into the indoor space. Among these ventilators there are those provided with a total heat exchanger, which performs heat exchange between the discharged air and the supplied air without mixing the two together. According to this type of ventilator, it is possible to suppress as much as possible the increase in air conditioning load due to taking non-temperature-adjusted outside air into the indoor space, while taking outside fresh air into the indoor space.
When used in cold regions, this type of ventilator has problems with freezing of devices or the like that are provided at positions where cold air passes through when outside air is taken in, because the outside air being taken in is cold.
As a countermeasure to this problem, in the ventilator disclosed in Japanese Laid-open Patent Application No. 2006-71225, for example, the air blowing rate is controlled such that the amount of discharged air after being temperature -adjusted in the indoor space is comparatively greater than the amount of cold air supplied from the outdoor space, and the aforementioned freezing problem is improved.
In the ventilator disclosed in Japanese Laid-open Patent Application No. 2006-2954, for example, part of the discharged air that has been temperature-adjusted in the indoor space is mixed with the supplied air in the vicinity of the intake port for outside cold air, raising the temperature of the supplied air and thereby improving the aforementioned problem.